Quote:
Originally Posted by NorCam
I use a Macs engine pivot (tilter) that bolts to the carb studs to lift engines. The thing really is slicker than snot for dropping engines down and positioning the mounts to drop right on. Adding the trans increases the load on those 4 studs and although this rig works awesome, I'm still a bit concerned about having it pull the carb studs and dropping an engine.
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Car looks great!
I also use that Macs Pivot Plate and love it!
One thing about how bolts and studs work...
Preload on the fastener = (torque)/(K*nominal diameter), where K is thread coefficient.
0.2 is a good K value for steel-on-steel. The higher the thread coefficient, the more thread friction we have. Let's say steel on aluminum is 0.3 (a wild conservative guess).
Let's say we have no gasket between that pivot plate and the manifold, so it is a rigid connection (the best way to use this plate). Let's also assume that we tighten the bolts holding the pivot plate to 15 ft-lbs (180 in-lbs). Let's calculate the preload in ONE of those studs / bolts:
(180)/(0.3*0.3125) = 1920 lbs.
That means that just ONE of those bolts has a theoretical preload of 1920 lbs. Four bolts would have a total clamp load of 7680 lbs. Until you exceed that clamp load, the fastener and threads do not actually see any additional load. If it doesn't pull threads when tightening the fastener, it's not going to load the threads more until you exceed 7680 lbs. Of course this assumes straight tension, and a completely rigid plate. Still, there is a ton of room for error here.
I used my Macs pivot plate to install an iron head BBC and TH400 in a Friends '70 Cutlass. No problems at all. As long as you tighten the bolts first, your chance of pulling threads is zero. 7680 lbs of clamp load also generates a lot of frictional force to keep the plate from sliding around and generating any side shear loading on the bolts.
Just throwing this out there for other guys nervous about carb plates.